You could do that, but just be sure you block it at the top. Blocking it anywhere lower will just cause more problems, i.e. more water & stuff gobbing up in the ducts & more rust. There was a guy in Mustang & Fords mag a few months ago (the really ugly pink and black stang cover car, if anyone remembers) who did a custom cowl panel to elminate the evil fresh air slots altogether. Not only did it look awesome, that would be the end-all for this problem. When I win the Power Ball, that's what I intend to have done to my 71.